Generally, such medical needle units include a needle unit like a butterfly needle structured by supporting the base end of the needle by a support member provided with a pair of wings, and such a needle unit is used by fixing the wings to a human body by an adhesive tape while inserting a needle into the human body. After such a needle is used, if the needle tip is left exposed, it may stick into other persons by mistake.
Therefore, there are needle units in which a cylindrical covering member is freely fitted to a tube that communicates and joins the needle and a medical container to each other, and after use, the needle unit is safely disposed of by covering the needle by the covering member (for example, refer to Patent Document 1).
Furthermore, there are needle units in which a holding member is movably and externally fitted with a covering member or a covering member is movably fitted to the inner side of the holding member so as to cover the needle after being used (for example, refer to Patent Documents 2 and 3).
However, these require a doctor or a nurse to move the covering member to the tip end of the needle to cover the needle, so that the operations are troublesome, and in addition, in a state that the needle is exposed, the covering member is movable toward the needle, so that after the needle is stuck into a human body, the covering member will move toward the tip end of the needle until the wings are fixed by tape. Furthermore, when moving the covering member to cover the needle, if the tape is not completely peeled off and still stuck between the covering member and the holding member, the covering member cannot move, which will be a problem.
Therefore, a needle unit is proposed in which the holding member is provided while leaving a space between the needle so that the covering member provided movably in the space between the holding member and the needle can automatically move from its housed posture to a covering posture by receiving an urging force of a spring, and the covering member moved to the covering posture is prevented from returning when it is pushed back (for example, refer to Patent Document 4).
However, because this returning prevention is realized by providing a return preventive guide so as to project in an elastically returnable manner near the terminal of the moving path of a projection provided on the covering member, the return preventive guide narrows the moving path of the projection, and the projection is required to forcibly move beyond the return preventive guide against the restoring force near the terminal of the movement of the covering member from the housed posture to the covering posture.
When the needle is thus covered by the covering member after the needle is used, in addition to the use in which the needle is pulled out from a patient and the engagement of the covering member in its housed posture is released to cover the needle, use in a slowly moving state so that the covering member in the housed posture is disengaged before pulling-out the needle from a patient and the needle is gradually pulled out while the tip end of the covering member is pressed against the skin of the patient, the needle is covered by the covering member in time with the pulling-out of the needle, and to reliably make the projection to forcibly move beyond the return preventive guide and turn into the covering posture even in such use, the urging force of the spring for moving the covering member to the covering posture sufficient to only move to the covering posture at the movement terminal from the housed posture is not sufficient, and an urging force for forcibly moving the covering member beyond the return preventive guide in the slowly moving state is necessary. Accordingly, the urging force of the spring becomes strong, and as a result, the covering member collides against the movement terminal and stops, and this causes not only a shock but also a loud collision noise and discomfort for the patient, the doctor, and the nurse.    [Patent Document 1] Japanese Published Unexamined Patent Application No. H11-319086    [Patent Document 2] Japanese Published Unexamined Patent Application No. H04-180772    [Patent Document 3] Japanese Published Unexamined Patent Application No. 2001-259029    [Patent Document 4] WO2003/074117    [Patent Document 5] Japanese Published Unexamined Patent Application No. H02-1289    [Patent Document 6] Japanese Published Unexamined Patent Application No. S63-317160